Recent advances in papermaking have improved the archival properties and the whiteness of paper, card and board. These advances are the result of various modifications including: replacement of yellowish rosin-derived sizes with less coloured, pH neutral or alkaline sizes such as alkyl ketene dimers or alkenylsuccinic acid anhydrides; replacement of acidic papermaking waters with pH neutral or slightly alkaline waters; and replacement of yellowish clay fillers with less coloured calcium carbonate fillers.
There remains a need for a method of imaging of substrates such as paper, card and board that shows effective marking in response to irradiation by laser light, but which also maintains the storage-stable near-whiteness of modern papers in unmarked areas, and also prior to marking.